Catalina Ponor wants to be the next Nadia Comaneci. At the Montreal Olympics in 1976, the 14-year-old Romanian gymnast revolutionized her sport by scoring the first-ever perfect 10.00 on the uneven bars, capturing hearts all over the world and launching an era of child gymnastics stars. Ponor, at 16, has superb balance and a rare clarity of artistic expression that recalls Comaneci. Whether she has Comaneci's effortless grace under pressure won't become clear until she competes in Athens, but Comaneci herself says Ponor has "everything it takes to be a champion." And Ponor leaves no doubt about her goal. "I have...